Portable devices capable of indicating a reference plane have been useful in the construction and carpentry trades, as well as in other applications, for some time. The advent of laser technology has seen the use of portable laser emitting devices capable of indicating a level 360-degree reference plane. For example, in the construction industry, narrow beams of collimated light, in the form of laser beams are being increasingly used in connection with establishing and marking long, straight, level lines, such as those required for markings for walls, ceilings, and/or floors. Also, laser beam projectors and receivers are often used in the construction industry and in agricultural land leveling applications to ensure that a target area is graded in the proper or desired slope or grade. The laser beam projector is placed in a known position and one or more sensors are placed in the targeted area to sense the impingement of the laser beam.
A lase emitting device that can generate a 360-degree reference plane typically includes a laser source for generating a beam of collimated light and a rotating mechanism for rotating the beam of light about an axis to generate a plane of light.
In order to provide a substantially level plane, it is necessary to have a known orientation for the laser plane with respect to the true earth reference. Typically, the laser plane is oriented perpendicular to the earth's gravitational field, such as by manually leveling the mechanism, or by a self-leveling mechanism though a corresponding pair of servo motors and inclinometer sensors. Additionally, some laser plane generators are operable to orient the laser plane at an angle with respect to the level orientation by rotating each or both of the axes according to the desire slope. While such laser projectors facilitate generating a laser plane at a desired grade and orientation, the higher number of moving parts, including the rotating mechanism, within the laser projector may raise reliability concerns over a prolonged period of time. Also, when sensors are not used to sense the laser beam, the reference plane generated by the rotated laser beam can be difficult to see with the human eye as the beam of light is intermittently flashed along a surface.
In some prior art tools, a 360-degree reference plane can be generated without a rotating mechanism, a laser beam is directed at a conical surface, such as a right angle cone whose optical surface is aligned with the axis of the laser beam.